Deposition of refractory metal films by rare-gas halide laser photodissociation of metal carbonyls

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Abstract
Films of Cr, Mo, and W on quartz, Pyrex, Suprasil, and Al substrates were deposited by photodissociation of the respective hexacarbonyls using focused and pulsed radiation from rare-gas halide lasers. Cr was deposited by dissociation of Cr(CO)6 using XeF (308 nm), KrF (249 nm), and ArF (193 nm) lasers. Mo and W were deposited from their respective hexacarbonyls at 249 and 193 nm. Pulse energies varied between 8 and 12 mJ. Pulse rates of 10–60 Hz were used. The pulse duration was about 10 ns. Depositions with substrates both parallel and perpendicular to the excimer radiation were attempted. Only in the case of perpendicular configuration were strongly adherent films observed. The deposition rates for thicknesses up to 3000 Å appeared to be independent of the pulse rate for all three metals. The films exhibited strong adhesion to the substrate. Scanning electron microscope photographs of the films revealed the presence of continuous metal layers. Auger and x-ray analyses of the films indicated contamination from carbon and oxygen. The source of these impurities is most likely to be CO produced in the decarbonylation of the parent hexacarbonyl. Adhesion to the substrate is apparently enhanced by laser stimulated generation of strong binding sites on the surface.